Electrode support structure assemblies

ABSTRACT

An electrode support structure assembly is provided comprising an electrode support structure including a plurality of splines. Each of the plurality of splines can have a proximal end portion and a distal end portion. The assembly further comprises a first element defining an axis and comprising an outer surface. The outer surface comprises a plurality of slots configured to receive the distal end portion of each of the plurality of splines. The first element is configured such that the distal end portion of each of the plurality of splines may move with respect to each slot. In accordance with some embodiments, the distal end portion of each of the plurality of splines comprises a section configured for engagement with the first element, wherein the section comprises a shoulder.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/340,760, filed 30 Dec. 2011 (the '760 application), now issued asU.S. Pat. No. 8,825,130. The '760 application is hereby incorporated byreference as though fully set forth herein.

BACKGROUND OF THE INVENTION

a. Field of the Invention

The instant disclosure relates generally to electrode support structureassemblies. In particular, the instant disclosure relates to electrodesupport structure assemblies for basket catheters including a pluralityof splines.

b. Background Art

Electrophysiology catheters are used in a variety of diagnostic,therapeutic, and/or mapping and ablative procedures to diagnose and/orcorrect conditions such as atrial arrhythmias, including for example,ectopic atrial tachycardia, atrial fibrillation, and atrial flutter.Arrhythmias can create a variety of conditions including irregular heartrates, loss of synchronous atrioventricular contractions and stasis ofblood flow in a chamber of a heart which can lead to a variety ofsymptomatic and asymptomatic ailments and even death.

Typically, a catheter is deployed and manipulated through a patient'svasculature to the intended site, for example, a site within a patient'sheart or a chamber or vein thereof. The catheter carries one or moreelectrodes that can be used for cardiac mapping or diagnosis, ablationand/or other therapy delivery modes, or both, for example. Once at theintended site, treatment can include, for example, radio frequency (RF)ablation, cryoablation, laser ablation, chemical ablation,high-intensity focused ultrasound-based ablation, microwave ablation,and/or other ablation treatments. The catheter imparts ablative energyto cardiac tissue to create one or more lesions in the cardiac tissueand oftentimes a contiguous or linear and transmural lesion. This lesiondisrupts undesirable cardiac activation pathways and thereby limits,corrals, or prevents errant conduction signals that can form the basisfor arrhythmias.

Various catheters and electrode arrangements can be employed fordifferent purposes. Catheters having basket-shaped electrode supportstructures are known and described in, for example and withoutlimitation, U.S. Pat. No. 5,772,590 entitled “Cardiovascular Catheterwith Laterally Stable Basket-Shaped Electrode Array with Puller Wire,”the entire disclosure of which is incorporated herein by reference asthough set forth in its entirety. Generally, catheters havingbasket-shaped electrode support structures are introduced through aguiding sheath with the electrode support structure in a folded orcollapsed position within the sheath so that the electrode supportstructure does not damage tissue during its introduction. Once thecatheter reaches its intended position within the heart, the guidingsheath can be removed and the electrode support structure can be allowedto radially outwardly expand for cardiac mapping or diagnosis, ablationand/or other therapy delivery modes, or both, for example.

Typically, basket-shaped electrode support structures comprise aplurality of splines that can be formed from laser cut tubing and beintegral at one end or that comprise discrete, separate elements. Thedistal ends of each of these plurality of splines generally must bejoined together. For example, the distal ends of each of the pluralityof splines can be mounted around a first piece of tubing and then beheld in place by a second piece of tubing as generally described andillustrated in U.S. Patent Application Publication No. 2007/0276212entitled “Basket Catheter With Improved Expansion Mechanism,” the entiredisclosure of which is hereby incorporated by reference as though setforth in its entirety.

It is desirable for each of the splines to be joined in such a way thatthe splines are configured to straighten evenly when the electrodesupport structure is collapsed. However, it may be difficult for theelectrode support structure to collapse evenly if manufacturingvariances have resulted in differences in the individual lengths of thesplines. It may also be difficult for the electrode support structure tocollapse evenly if one or more of the splines have experienced a changein length relative to the remainder of the splines, such as duringmanipulation of the electrode support structure around a curve, forexample. If the splines do not straighten evenly when the electrodesupport structure is collapsed, a protrusion or “loop” can form at thedistal end of one or more of the plurality of splines. Continuedcollapse or multiple collapses of the electrode support structure canpotentially cause fatigue at the point of the protrusion or “loop” andultimately fracture the spline. Moreover, when the distal ends of thesplines are fixed in place (e.g., mounted between two pieces of tubing),the distal flexibility of the splines may be limited, thereby adverselyimpacting the collapsibility of the electrode support structure. Inaddition, stress imparted at the distal end of the electrode supportstructure during collapse and/or expansion of the electrode supportstructure can also result in the failure of any strut or other elementthat may be configured to join the distal ends of the splines together.

Additionally, when the electrode support structure is in an expandedstate, electrode distribution may not be uniform in accordance with someelectrode arrangements. Moreover, during collapse of the electrodesupport structure (e.g., when the electrode support structure isemerging from or being retracted into a delivery sheath), some electrodearrangements may possibly result in electrode to electrode contactand/or short circuits, which may cause electrode wear and/or limitelectrode functionality. In addition, some electrode arrangements maynot minimize the profile of the electrode support structure duringcollapse of the electrode support structure, which can result inelectrode damage when the electrode support structure is being deliveredthrough the delivery sheath, especially when being delivered through atortuously angulated pathway.

Typically, basket-shaped electrode support structures can include anexpander having a distal end attached to a distal end of the electrodesupport structure. The expander includes a proximal end that extends outof a proximal end of a catheter or other medical device employing theelectrode support structure to a control handle. The expander can bemoved longitudinally relative to the catheter or other medical device toexpand and contract the electrode support structure. The expander isgenerally coaxial with the catheter. An expander will not generallyallow for free axial movement of the electrode support structure if theelectrode support structure is being diametrically constrained in someway.

There is therefore a need to minimize and/or eliminate one or more ofthe problems as set forth above. The foregoing discussion is intendedonly to illustrate the present field and should not be taken as adisavowal of claim scope.

BRIEF SUMMARY OF THE INVENTION

It is desirable to provide an electrode support structure assembly thatcan include an element joining the distal end of each of the pluralityof splines that is configured to provide freedom for each of theplurality of splines to move independently along an axis of theelectrode support structure. This may help ensure that the splines areconfigured to straighten evenly when the electrode support structure iscollapsed. It is also desirable to provide an electrode supportstructure assembly that can include an element joining the distal end ofeach of the plurality of splines that is configured to provide freedomfor each of the plurality of splines to articulate relative to an axisof the electrode support structure such that each of the plurality ofsplines can be positioned at numerous angles relative to the axis of theelectrode support structure in order to minimize stress imparted at thedistal end of the electrode support structure during collapse and/orexpansion. It is also desirable to provide an improved electrodearrangement that may provide more uniform electrode distribution whenthe electrode support structure is in its deployed or expanded state,while at the same time providing a smaller profile when in a collapsedstate so as prevent electrode to electrode short circuits. It is alsodesirable to provide an electrode support structure that can beconfigured to allow for free, uniform axial displacement even if theelectrode support structure is being diametrically constrained in someway.

An electrode support structure assembly is provided comprising anelectrode support structure comprising a plurality of splines and afirst element. Each of the plurality of splines can have a proximal endportion and a distal end portion opposing the proximal end portion. Thefirst element can define an axis and comprise an outer surface. Theouter surface can comprise a plurality of slots configured to receivethe distal end portion of each of the plurality of splines. The firstelement is configured such that the distal end portion of each of theplurality of splines may move with respect to each slot. In accordancewith some embodiments, the distal end portion of each of the pluralityof splines comprises a section configured for engagement with the firstelement, wherein the section comprises a shoulder. In other words, adistal end of the distal end portion of each of the plurality of splinescan have an increased diameter relative to the remainder of the distalend portion of each of the plurality of splines.

In accordance with a first embodiment of the disclosure, the firstelement comprises a generally cylindrical member and the plurality ofslots comprise grooves on the outer surface. The grooves can extendalong the axis of the first element and can be configured to allow eachof the plurality of splines to move along the axis of the first elementa select distance. Still in accordance with a first embodiment of thedisclosure, the electrode support structure assembly can furthercomprise a second element configured for engagement with the firstelement to retain the distal end portion of each of the plurality ofsplines within the plurality of slots of the first element. The secondelement can comprise a cap having at least a portion thereof configuredto be disposed radially outwardly of the first element. The cap canfurther comprise an axial end. The axial end can be separated from thefirst element by a select distance to allow for movement of each of theplurality of splines along the axis of the first element. In accordancewith some embodiments of the disclosure, the electrode support structureassembly can further include a third element comprising a generallycylindrical member having an outer radial surface including a pluralityof channels configured to receive the proximal end portion of each ofthe plurality of splines. The proximal end portion of each of theplurality of splines can comprise a section configured for engagementwith the third element, wherein the section comprises a shoulder. Aproximal end of the proximal end portion of each of the plurality ofsplines can have an increased diameter relative to the remainder of theproximal end portion of each of the plurality of splines in accordancewith some embodiments of the disclosure.

In accordance with a second embodiment of the disclosure, the firstelement can comprise a cap having an axial end and a radially extendingwall. Each of the plurality of slots can extend through the radiallyextending wall. Each of the plurality of slots can extend along the axisof the first element. Each of the plurality of slots can be configuredto allow each of the plurality of splines to articulate from a firstposition in which the distal end portion of the spline is disposed at afirst angle relative to the axis of the first element to a secondposition in which the distal end portion of the spline is disposed at asecond angle relative to the axis of the first element, wherein thefirst angle is different than the second angle. The cap furthercomprises an axial end separated from the second element by a selectdistance to allow for movement of each of the plurality of splines.Still in accordance with a second embodiment of the disclosure, theelectrode support structure assembly can further comprise a secondelement configured for engagement with the first element to retain thedistal end portion of each of the plurality of splines within theplurality of slots of the first element. The second element can comprisea generally cylindrical member with an outer radial surface having atleast a portion thereof configured to be disposed radially inwardly ofthe first element. In particular, the second element can comprise afluid coupler having a first end configured to mate with the firstelement and a second end configured to mate with a tubing assembly.

In accordance with some embodiments of the disclosure, the plurality ofsplines includes a first spline and a second spline. The first splinecan include a first plurality of electrodes spaced apart on the firstspline, and the second spline can include a second plurality ofelectrodes spaced apart on the second spline. In accordance with someembodiments of the disclosure, the first plurality of electrodes can besubstantially evenly spaced apart on the first spline, and the secondplurality of electrodes can be substantially evenly spaced apart on thesecond spline. Each of the second plurality of electrodes on the secondspline can be in a staggered position relative to the position of eachof the first plurality of electrodes on the first spline. For exampleand without limitation, at least one of the second plurality ofelectrodes on the second spline can be located on the second spline at aposition that is in substantially the same plane as the midpoint betweentwo of the first plurality of electrodes on the first spline. A firstdistance between a distal-most electrode of the first plurality ofelectrodes and a distal end of the first spline can be substantially thesame as a second distance between a proximal-most electrode of thesecond plurality of electrodes and a proximal end of the second splinein accordance with some embodiments of the disclosure.

An electrode support structure assembly in accordance with a thirdembodiment of the disclosure is also provided. The assembly includes anelectrode support structure comprising a proximal end and a distal endand defining longitudinal axis. The electrode support structure isconfigured to be radially outwardly expandable relative to thelongitudinal axis to an expanded arrangement and radially inwardlycollapsible relative to the longitudinal axis to a collapsedarrangement. The electrode support structure can further include aplurality of splines. Each of the plurality of splines can have aproximal end portion and a distal end portion opposing the proximal endportion. The distal end portion of each of the plurality of splines cancomprise a first connection element configured to connect the distal endportion to a first adjacent spline; and a second connection elementconfigured to connect the distal end portion to a second adjacentspline, wherein the first connection element, second connection element,and each of the plurality of splines are integrally formed. In addition,at least a portion of the distal end portion of each of the plurality ofsplines can be disposed substantially along the longitudinal axis of theelectrode support structure. The electrode support structure assemblycan further comprise a sheath. Movement of the proximal end of theelectrode support structure relative to the sheath can be configured toexpand and collapse the electrode support structure.

The foregoing and other aspects, features, details, utilities, andadvantages of the present disclosure will be apparent from reading thefollowing description and claims, and from reviewing the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a catheter system employing an electrodesupport structure assembly in accordance with a first embodiment of thedisclosure.

FIG. 2 is a lateral elevational view of an electrode support structureassembly in accordance with a first embodiment of the disclosure.

FIG. 3 is a close-up, perspective cross-sectional view of a portion ofthe electrode support structure assembly of FIG. 2.

FIG. 4 is a perspective view of an electrode support structure assemblyin accordance with a second embodiment of the disclosure.

FIG. 5 is a distal isometric view of the electrode support structureassembly of FIG. 4.

FIG. 6 is an isometric, cross-sectional view of the distal end of theelectrode support structure assembly of FIG. 4.

FIG. 7 is a cross-sectional view of the distal end of the electrodesupport structure assembly of FIG. 4.

FIG. 8 is a perspective view of a proximal element of the electrodesupport structure assembly of FIG. 4.

FIG. 9 is a cross-sectional view of the proximal end of the electrodesupport structure assembly of FIG. 4.

FIG. 10 is a lateral elevational view of an electrode support structurehaving an improved electrode arrangement in accordance with a thirdembodiment of the disclosure.

FIG. 11 is a lateral elevational view of a portion of the electrodesupport structure of FIG. 10.

FIGS. 12A-12C are lateral elevational views of an electrode supportstructure in accordance with a fourth embodiment of the disclosureillustrating the deployment of the electrode support structure.

FIG. 13 is a close-up view of a distal end of the electrode supportstructure of FIGS. 12A-12C.

DETAILED DESCRIPTION OF THE DISCLOSURE

Various embodiments are described herein to various apparatuses,systems, and/or methods. Numerous specific details are set forth toprovide a thorough understanding of the overall structure, function,manufacture, and use of the embodiments as described in thespecification and illustrated in the accompanying drawings. It will beunderstood by those skilled in the art, however, that the embodimentsmay be practiced without such specific details. In other instances,well-known operations, components, and elements have not been describedin detail so as not to obscure the embodiments described in thespecification. Those of ordinary skill in the art will understand thatthe embodiments described and illustrated herein are non-limitingexamples, and thus it can be appreciated that the specific structuraland functional details disclosed herein may be representative and do notnecessarily limit the scope of the embodiments, the scope of which isdefined solely by the appended claims.

Reference throughout the specification to “various embodiments,” “someembodiments,” “one embodiment,” or “an embodiment”, or the like, meansthat a particular feature, structure, or characteristic described inconnection with the embodiment is included in at least one embodiment.Thus, appearances of the phrases “in various embodiments,” “in someembodiments,” “in one embodiment,” or “in an embodiment”, or the like,in places throughout the specification are not necessarily all referringto the same embodiment. Furthermore, the particular features,structures, or characteristics may be combined in any suitable manner inone or more embodiments. Thus, the particular features, structures, orcharacteristics illustrated or described in connection with oneembodiment may be combined, in whole or in part, with the featuresstructures, or characteristics of one or more other embodiments withoutlimitation given that such combination is not illogical ornon-functional.

It will be appreciated that the terms “proximal” and “distal” may beused throughout the specification with reference to a clinicianmanipulating one end of an instrument used to treat a patient. The term“proximal” refers to the portion of the instrument closest to theclinician and the term “distal” refers to the portion located furthestfrom the clinician. It will be further appreciated that for concisenessand clarity, spatial terms such as “vertical,” “horizontal,” “up,” and“down” may be used herein with respect to the illustrated embodiments.However, surgical instruments may be used in many orientations andpositions, and these terms are not intended to be limiting and absolute.

The instant disclosure generally relates to electrode supportstructures. For purposes of this description, similar aspects among thevarious embodiments described herein will be referred to by similarreference numbers. As will be appreciated, however, the structure of thevarious aspects can be different among the various embodiments.

Referring now to FIG. 1, a side view of an intracardiac catheter system10 employing an electrode support structure assembly 12 in accordancewith a first embodiment of the disclosure is generally illustrated. Thecatheter system 10 includes a handle 14 and connectors 16 disposedproximal to the handle 14 for making electrical connections to avisualization, navigation, and/or mapping system (not shown) such asthose systems available under the name ENSITE NAVX™ (aka ENSITE™ Classicas well as newer versions of the ENSITE™ system, denoted as ENSITEVELOCITY™) and available from St. Jude Medical, Inc. The handle 14 canhave a uni-directional design, a bi-directional design, or any othersuitable design and be accordingly configured to steer the electrodesupport structure assembly 12. The catheter system 10 can also includean introducer 18 located distally of the handle 14 that may be used todeliver an elongated catheter body 20 into the body of a patient,through a hemostasis valve of another, longer introducer, for example.The elongated catheter body 20 can extend from the introducer 18. Theelectrode support structure assembly 12 is configured to extend from thedistal end of the elongated catheter body 20. The elongated catheterbody 20 can comprise an elongated tubular construction having one ormore lumens. The elongated catheter body 20 can be flexible or bendable.The elongated catheter body 20 can be of any suitable construction andmade of any suitable material as known to those of ordinary skill in theart. The elongated catheter body 20 can have any outer diameter, but maygenerally be less than about 8 French. The elongated catheter body 20can have an outer wall of any thickness, but may generally be configuredso that one or more lumens can be disposed within the elongated catheterbody 20 to accommodate pull wires, lead wires, sensor cables, and anyother wires, cable, and/or tubes that may be needed in particularapplications. The handle 14, connectors 16, introducer 18, and elongatedcatheter body 20 can be readily modified as dictated by the aesthetic orfunctional needs of particular applications. Although the electrodesupport structure assembly 12 is described and illustrated in connectionwith an intracardiac catheter system 10, the electrode support structureassembly 12 may be utilized in connection with other types of medicaldevices, such as for example and without limitation, stone retrievalbaskets, distal protection devices, renal artery ablation devices,snares, and other retrieval devices.

Referring now to FIG. 2, an elevational view of the electrode supportstructure assembly 12 in accordance with a first embodiment of thedisclosure is generally illustrated. The electrode support structureassembly 12 is mounted to the distal end of the elongated catheter body20. The electrode support structure assembly 12 comprises an electrodesupport structure 22. The electrode support structure 22 defines alongitudinal axis (A). The electrode support structure 22 comprises aplurality of splines 24. The splines 24 are deflectable elongatedelements. The plurality of splines 24 can be configured to assumedifferent configurations. For example and without limitation, theelectrode support structure 22 can comprise a “basket” in which each ofthe plurality of splines 24 can splay or bow radially outwardly. Theparticular shape of the “basket” can vary. For example and withoutlimitation, one or more of the plurality of splines 24 can splay or bowradially outwardly substantially uniformly along the length of theelectrode support structure 22, away from longitudinal axis (A), or oneor more of the plurality of splines 24 can splay or bow radiallyoutwardly in varying amounts along the length of the electrode supportstructure 22. The resulting “basket” is generally symmetric about thelongitudinal axis (A) of the electrode support structure 22 inaccordance with some embodiments of the disclosure. As used herein, theterm “basket” is not limited to the illustrated configuration, but caninclude other designs such as spherical or egg-shaped designs, forexample. Although a “basket” shape is mentioned in detail, the pluralityof splines 24 can assume any number of other shapes in accordance withvarious embodiments of the disclosure.

Each of the plurality of splines 24 can comprise a flexible wire with anon-conductive covering in accordance with some embodiments of thedisclosure. The flexible wire can comprise a flat Nitinol wire inaccordance with some embodiments of the disclosure. The non-conductivecovering can comprise a biocompatible plastic tubing, such aspolyurethane or polyimide tubing in accordance with some embodiments ofthe disclosure. Although these materials are mentioned in detail, thesplines 24 can be made of any other suitable materials known to those ofordinary skill in the art. For example and without limitation, thesplines 24 can be designed without internal flexible wires if asufficiently rigid non-conductive material is used. The electrodesupport structure assembly 12 can further comprise one or moreelectrodes 54 supported by one or more of the plurality of splines 24.For example, one or more of the plurality of splines 24 can have one ormore electrodes 54 mounted on the non-conductive covering in accordancewith various embodiments of the disclosure. The number and spacing ofthe electrodes 54 on the plurality of splines 24 can vary in accordancewith various embodiments of the disclosure.

Each of the plurality of splines 24 has a proximal end portion 26 and adistal end portion 28 opposing the proximal end portion 26 as best shownin FIGS. 2-3. For example and without limitation, the electrode supportstructure 22 may include eight splines 24. Although eight splines 24 arementioned in detail, there may be fewer or more splines 24 in accordancewith various embodiments of the disclosure. Each of the plurality ofsplines 24 may generally be evenly spaced circumferentially around theaxis (A) of the electrode support structure 22.

The electrode support structure 22 is configured to be radiallyoutwardly expandable relative to its axis (A) to an expanded arrangementas shown in FIGS. 1-3. The electrode support structure 22 is alsoconfigured to be radially inwardly collapsible relative to its axis (A)to a collapsed arrangement. The plurality of splines 24 of the electrodesupport structure 22 can be collapsed by an application of force. Uponremoval of the application force, the plurality of splines 24 may returnto the expanded arrangement. This expansion and collapse of theelectrode support structure 22 may be achieved by using a shape memorymaterial for the plurality of splines 24 in accordance with someembodiments of the disclosure. The expansion and collapse of theelectrode support structure 22 may be achieved by using a biasingmechanism in accordance with other embodiments of the disclosure. Forexample and without limitation, an expander or tensor (not shown) may becoaxial with the elongated catheter body 20. The expander or tensor canhave a distal end at the distal end portion 28 of the electrode supportstructure 22 and a proximal end extending out the proximal end of theelongated catheter body 20 and attached to the control handle 14.Longitudinal movement of the tensor relative to the elongated catheterbody 20 can cause expansion and contraction of the electrode supportstructure 22. The tensor can comprise any material sufficiently rigid toachieve this function.

The electrode support structure assembly 12 further comprises a firstelement 30. Referring now to FIG. 3, the first element 30 is a generallycylindrical member having an axis (a). The first element 30 comprises anouter radial surface 32 located about the axis (a). The outer radialsurface 32 includes a plurality of slots. The plurality of slots aresubstantially evenly circumferentially spaced around the outer radialsurface 32 of the first element 30. Each of the plurality of slots isconfigured to receive the distal end portion 28 of each of the pluralityof splines 24. In accordance with an embodiment of the disclosure, eachof the plurality of slots can comprise grooves 34 on the outer radialsurface 32 in which the splines 24 can be slidingly disposed. Thegrooves 34 can extend along the axis (a) of the first element 30. Thegrooves 34 can be configured to allow each of the plurality of splines24 to move (e.g., slide) along the axis (a) of the first element 30 aselect distance (d). Accordingly, the first element 30 is configured toprovide freedom for the splines 24 to move independently along the axis(a) of the first element 30. For example and without limitation, thefirst element 30 may be configured to allow each of the plurality ofsplines 24 to independently, axially travel a distance (d) from 0 toabout 0.100 inches (about 2.54 mm). Although this particular range fordistance (d) is mentioned in detail, the first element 30 may beconfigured to allow each of the plurality of splines 24 toindependently, axially travel a distance (d) that is greater or smallerin accordance with other embodiments of the disclosure.

The distal end portion 28 of each of the plurality of splines 24 cancomprise a section configured to restrain the axial slide movement ofeach of the plurality of splines 24 so as to keep each of the pluralityof splines 24 within the first element 30 of the electrode supportstructure assembly 12. For example and without limitation, the sectionof the distal end portion 28 can comprise a shoulder 36. In other words,a distal end 38 of the distal end portion 28 of each of the plurality ofsplines 24 has an increased diameter relative to the remainder of thedistal end portion 28 of each of the plurality of splines 24, therebyforming the shoulder 36 in each of the plurality of splines 24.

Referring now to FIGS. 2-3, the electrode support structure assembly 12further comprises a second element 40. Second element 40 is configuredfor engagement with the first element 30 to retain the distal endportion 28 of each of the plurality of splines 24 within the pluralityof slots on the first element 30. In accordance with the firstembodiment of the disclosure as generally illustrated in FIGS. 2-3, thesecond element 40 comprises a cap having at least a portion thereof thatis configured to be disposed radially outwardly of the first element 30.Accordingly, the cap 40 can be configured to radially and/or axiallyconfine each of the plurality of splines 24. The cap 40 furthercomprises an axial end 42 in accordance with some embodiments of thedisclosure. The axial end 42 of the cap 40 is separated from the firstelement 30 by a select distance (D1) to allow for movement of each ofthe plurality of splines 24 along the axis (a) of the first element 30.Although the second element 40 is described and illustrated as a cap,the second element 40 can comprise a ring in accordance with otherembodiments of the disclosure. The ring can be configured to radiallyconfine the plurality of splines 24 and also allow for movement of eachof the plurality of splines 24 along the axis (a) of the first element30.

Referring back to FIG. 2, in accordance with some embodiments of thedisclosure, the electrode support structure assembly 12 can furthercomprise a third element 44. The third element 44 can comprise agenerally cylindrical member having an outer radial surface 46 includinga plurality of channels 48. Each of the plurality of channels 48 can beconfigured to receive the proximal end portion 26 of each of theplurality of splines 24. The channels 48 can extend along the axis (A)of the electrode support structure 22. The channels 48 can be configuredto allow each of the plurality of splines 24 to move (e.g., slide) alongthe axis (A) of the electrode support structure 22. Accordingly, thethird element 44 is configured to provide freedom for the splines 24 tomove independently along the axis (A) of the electrode support structure22. For example and without limitation, the third element 44 may beconfigured to allow each of the plurality of splines 24 toindependently, axially travel a distance from 0 to about 0.100 inches(about 2.54 mm). Although this particular range for the distance ismentioned in detail, the third element 42 may be configured to alloweach of the plurality of splines 24 to independently, axially travel adistance that is greater or smaller in accordance with other embodimentsof the disclosure.

The proximal end portion 26 of each of the plurality of splines 24 cancomprise a section configured to restrain the axial slide movement ofeach of the plurality of splines 24 so as to keep each of the pluralityof splines 24 within the third element 42 of the electrode supportstructure assembly 12. For example and without limitation, the sectionof the proximal end portion 26 can comprise a shoulder 50. In otherwords, a proximal end 52 of the proximal end portion 26 of each of theplurality of splines 24 has an increased diameter relative to theremainder of the proximal end portion 26 of each of the plurality ofsplines 24, thereby forming the shoulder 50 in each of the plurality ofsplines 24.

Referring now to FIGS. 4-9, an electrode support structure assembly 112in accordance with a second embodiment of the disclosure is generallyillustrated. The electrode support structure assembly 112 can besimilarly mounted to the distal end of the elongated catheter body 20(see FIG. 1) and can be substantially identical to electrode supportstructure assembly 12 described above except for differences in theproximal end portion of each of the plurality of splines and differencesin the elements configured to join the distal end portions of thesplines as described hereinbelow. The electrode support structureassembly 112 can further comprise one or more electrodes (such aselectrodes 54 shown in FIG. 2) supported by one or more of the pluralityof splines 124. For example, one or more of the plurality of splines 124can have one or more electrodes (such as electrodes 54 shown in FIG. 2)mounted on the non-conductive covering of each of the plurality ofsplines 124 in accordance with various embodiments of the disclosure.The number and spacing of the electrodes (such as electrodes 54 shown inFIG. 2) on the plurality of splines 124 can vary in accordance withvarious embodiments of the disclosure.

The electrode support structure assembly 112 comprises a first element130. Referring now to FIGS. 5-7 in particular, the first element 130 maybe a cap having an axis (a) about which an outer radial surface 132extends. The outer radial surface 132 of the first element 130 includesa plurality of slots 134. The outer radial surface 132 may be part of aradially extending wall 135. The cap 130 can further include an axialend 137. The axial end 137 can be separated from the second element 140by a select distance D₂ (see FIG. 7) to allow for movement (e.g., distalarticulation) of each of the plurality of splines 124. The plurality ofslots 134 are substantially evenly circumferentially spaced around theouter radial surface 132 of the first element 130. Each of the pluralityof slots 134 is configured to receive the distal end portion 128 of eachof the plurality of splines 124. In accordance with an embodiment of thedisclosure, each of the plurality of slots 134 can extend through theradially extending wall 135. Each of the plurality of slots 134 canextend parallel to or along the axis (a) of the first element 130.

Referring now to FIG. 7, each of the plurality of slots 134 isconfigured to allow each of the plurality of splines 124 to articulatefrom a first position P₁ in which the distal end portion 128 of thespline 124 is disposed at a first angle α relative to the axis (a) ofthe first element 130 to a second position P₂ (shown in dotted lines) inwhich the distal end portion 128 of the spline 124 is disposed at asecond angle β relative to the axis (a) of the first element 130. Thefirst angle α is different than the second angle β in accordance withvarious embodiments of the disclosure. For example and withoutlimitation, position P₁ corresponds to the electrode support structure122 in an expanded arrangement and position P₂ corresponds to theelectrode support structure 122 in a collapsed arrangement. Under suchcircumstances, the first angle α is greater than the second angle β. Theslots 134 are configured to allow each of the plurality of splines 124to articulate relative to the axis (a) of the first element 130Accordingly, the first element 130 is configured to provide freedom forthe splines 124 to distally articulate relative to the axis (a) of thefirst element 130, thereby allowing for increased distal flexibility ofthe electrode support structure 122, improved collapsibility of theelectrode support structure 122, and decreased axial and radialresistive force which might otherwise result in failure at the distalend of the electrode support structure assembly 112.

The distal end portion 128 of each of the plurality of splines 124 cancomprise a section configured to retain each of the plurality of splines124 within the first element 130 of the electrode support structure 112.For example and without limitation, the section of the distal endportion 128 can comprise a shoulder 136. In other words, a distal end138 of the distal end portion 128 of each of the plurality of splines124 has an increased diameter relative to the remainder of the distalend portion 128 of each of the plurality of splines 124, thereby formingthe shoulder 136 in each of the plurality of splines 124.

Referring now to FIGS. 4-7, the electrode support structure assembly 112comprises a second element 140 configured for engagement with the firstelement 130 to retain the distal end portion 128 of the each of theplurality of splines 124 within the plurality of slots 134 of the firstelement 130. In accordance with the second embodiment of the disclosureas generally illustrated in FIGS. 4-7, the second element 140 comprisesa generally cylindrical member 140 with an outer radial surface 141having at least a portion thereof configured to be disposed radiallyinwardly of the first element 130. The second element 140 can comprise afluid coupler having a first end portion 143 (see FIG. 6) configured tomate with the first element 130 and a second end portion 145 (see FIG.6) configured to mate with a tubing assembly (not shown). The tubingassembly may be connected to an irrigation system and include, forexample and without limitation, an irrigation pump and can be configuredto supply irrigation fluid to the fluid coupler, the fluid couplerconfigured to transfer the fluid to the electrode support structureassembly 112 at the distal end of the assembly. The fluid coupler 140can also be configured to radially confine the plurality of splines 124.

Referring now to FIGS. 4 and 8-9, in accordance with some embodiments ofthe disclosure, the electrode support structure assembly 112 can furthercomprise a third element 42. The third element 42 can comprise agenerally cylindrical member having an outer radial surface 44 includinga plurality of channels 146. Each of the plurality of channels 46 can beconfigured to receive the proximal end portion 126 of each of theplurality of splines 124. The channels 146 can extend parallel to oralong the axis (A) of the electrode support structure 122. Referring nowto FIG. 9, in accordance with an embodiment of the disclosure, theproximal end portion 126 of each of the plurality of splines 124 can beformed by laser cutting a tube, such that the proximal end portion 126of each of the plurality of splines 124 are integral. Although theproximal end portion 126 of each of the plurality of splines 124 aredescribed and illustrated as being formed by laser cutting a tube, suchas a metallic Nitinol tube, the proximal end portions 126 of each of theplurality of splines 124 may be independently moveable at a proximal endas described and illustrated in connection with the first embodiment ofthe disclosure.

Referring now to FIGS. 10-11, each of the plurality of splines 24, 124can have one or more electrodes 54 mounted on the non-conductivecovering in accordance with some embodiments of the disclosure.Reference herein to splines 24 includes one or more of splines 24 ₁and/or 24 ₂. Reference herein to splines 124 includes one or more of 124₁ and/or 124 ₂. The electrodes 54 mounted on each of the plurality ofsplines 24, 124 can comprise ring electrodes in accordance with anembodiment of the disclosure. Each of the electrodes 54 on the splines24, 124 is electrically connected to the visualization, navigation,and/or mapping system (not shown) such as those systems available underthe name ENSITE NAVX™ (aka ENSITE™ Classic as well as newer versions ofthe ENSITE™ system, denoted as ENSITE VELOCITY™) and available from St.Jude Medical, Inc. (not shown) and/or a source of ablation energy bymeans of an electrode lead wire (not shown). Each electrode lead wireextends through the control handle 14, through a lumen in the elongatedcatheter body 20, and into the non-conductive covering of acorresponding spline 24, 124. Each lead wire is attached to itscorresponding electrode 54 by any suitable method known to those ofordinary skill in the art. An exemplary method for attaching a lead wireto an electrode 54 involves making a small hole through the wall of thenon-conductive covering. For example and without limitation, a needlemay be inserted through the non-conductive covering and heatedsufficiently to form a permanent hole. The lead wire can then be drawnthrough the hole by using a microhook or similar structure. The leadwire can then be stripped of any coating and welded to the underside ofthe electrode 54, which can then be slid into position over the hole andfixed in place with polyurethane glue or the like. Alternatively, eachelectrode 54 can be formed by wrapping a lead wire around thenon-conductive covering a number of times and stripping the lead wire ofits own insulated coating on radially outwardly extending surfaces.

One or more of the splines 24, 124 can include at least one electrode54. Reference herein to electrode 54 includes one or more of electrodes54 ₁ and/or 54 ₂. In various embodiments, each spline 24, 124 caninclude multiple electrodes 54 spaced along substantially the entirelength of the spline 24, 124. The electrodes 54 along a spline 24, 124or along each of the plurality of splines 2, 124 may be the same ordifferent in size. In accordance with a third embodiment of thedisclosure, the electrode support structure assembly 12, 112 comprisesan electrode support structure 22, 122 including an even number ofsplines 24, 124. Each of the plurality of splines 24, 124 can include anequal number of electrodes 54 disposed thereon. Each of the electrodes54 can be substantially evenly spaced along the length of each of theplurality of splines 24, 124. In accordance with the third embodiment ofthe disclosure, the plurality of splines 24, 124 includes at least afirst spline 24 ₁, 124 ₁ and a second spline 24 ₂, 124 ₂. The firstspline 24 ₁, 124 ₁ includes a first plurality of electrodes 54 ₁substantially evenly spaced apart on the first spline. The distancebetween adjacent electrodes 54 ₁ on the first spline 24 ₁, 124 ₁ may bea selected length (l). The second spline 24 ₂, 124 ₂ includes a secondplurality of electrodes 54 ₂ substantially evenly spaced apart on thesecond spline. The distance between adjacent electrodes 54 ₂ on thesecond spline 24 ₂, 124 ₂ may be a selected length (l) substantiallyequal to the selected length (l) between adjacent electrodes 54 ₁ on thefirst spline 24 ₁, 124 ₁. Each of the second plurality of electrodes 54₂ on the second spline 24 ₂, 124 ₂ is in a staggered position relativeto the position of each of the first plurality of electrodes 54 ₁ on thefirst spline 24 ₁, 124 ₁. In particular, at least one of the secondplurality of electrodes 54 ₂ on the second spline 24 ₂, 124 ₂ is locatedon the second spline 24 ₂, 124 ₂ at a position that is substantially ina plane that is transverse to a longitudinal axis of the second spline24 ₂, 124 ₂ and containing the midpoint (m) between two of the firstplurality of electrodes 54 ₁ on the first spline 24 ₁, 124 ₁.Accordingly, the electrodes 54 ₁, 54 ₂ are positioned alternately suchthat the electrodes 54 ₁, 54 ₂ on adjacent splines 24 ₁, 124 ₁, 24 ₂,124 ₂ do not coincide with each other, but fall within the middle of thespace of length (l) between electrodes 54 ₁, 54 ₂ on the adjacent spline24 ₁, 124 ₁, 24 ₂, 124 ₂

An electrode arrangement in accordance with the third embodiment of thedisclosure may provide for more uniform electrode distribution about asurface of the spheroid formed by the electrode support structure 22,122, thereby potentially resulting in improved mapping. An electrodearrangement in accordance with the third embodiment of the disclosuremay also be configured to prevent electrode to electrode short circuitswhen the electrode support structure 22, 122 is in its collapsed orpartially collapsed state (e.g., when emerging from or being pulled into a delivery sheath). An electrode arrangement in accordance with thethird embodiment of the disclosure may also allow a smaller profile whenthe electrode support structure 22, 122 is being delivered through atortuously angulated pathway.

In accordance with the third embodiment of the disclosure, each spline24 ₁, 124 ₁, may be symmetric with each adjacent spline 24 ₂, 124 ₂. Inother words, each spline 24 ₁, 124 ₁, 24 ₂, 124 ₂ can have the sameelectrode layout when flipped proximal end to distal end. In accordancewith such an arrangement, a first distance dist₁ between a distal-mostelectrode 54 _(d) of the first plurality of electrodes 54 ₁ and a distalend 28 ₁ of the first spline 24 ₁, 124 ₁ is substantially the same as asecond distance dist₂ between a proximal-most electrode 54 _(p) of thesecond plurality of electrodes 54 ₂ and a proximal end 26 ₂ of thesecond spline 24 ₂, 124 ₂. Although these particular electrodearrangements are mentioned and illustrated in detail, there may beadditional electrode arrangements that be utilized in accordance withvarious embodiments of the disclosure. For example and withoutlimitation, spacing between electrodes 54 can vary based on the lengthof splines 24 ₁, 124 ₁, 24 ₂, 124 ₂ or the desired distance from theproximal and distal ends 26, 28 of the splines 24 ₁, 124 ₁, 24 ₂, 124 ₂.

In accordance with a fourth embodiment of the disclosure and withreference to FIGS. 12A-12C, an electrode support structure assembly 212including an electrode support structure 222 and a sheath 227 isgenerally illustrated. The electrode support structure assembly 212 inaccordance with the fourth embodiment of the disclosure can beconfigured to better provide for diametric collapse disproportionate toaxial retraction, which may allow for free, uniform axial displacementeven when the electrode support structure assembly 212 is beingdiametrically constrained in some way. Each of the plurality of splines224 forming the electrode support structure 222 can comprise a Nitinolwire with a non-conductive covering (not shown), such as polyurethane orpolyimide tubing, and electrodes (not shown) interspersed along thesplines 224, as described above. Although these materials are mentionedin detail, the splines 224 can be made of any other suitable materialsknown to those of ordinary skill in the art. Each of the plurality ofsplines 224 has a proximal end portion 226 and a distal end portion 228opposing the proximal end portion 226. For example and withoutlimitation, the electrode support structure 222 may include eightsplines 224. Although eight splines 224 are mentioned in detail, theremay be fewer or more splines 224 in accordance with various embodimentsof the disclosure. Each of the plurality of splines 224 may generally beevenly spaced circumferentially around a longitudinal axis (A) definedby the electrode support structure 222. The electrode support structure222 is configured to be radially outwardly expandable relative to itsaxis (A) to an expanded arrangement as shown in FIG. 12C. The electrodesupport structure 222 is also configured to be radially inwardlycollapsible relative to its axis (A) to a collapsed arrangement as shownin FIG. 12A. The expansion and collapse of the electrode supportstructure 222 may be achieved using a shape memory material having apreset shape for the plurality of splines 224 in accordance with thefourth embodiment of the disclosure. Accordingly, no separate mechanicalbiasing mechanism, such as an expander or tensor, may be needed inaccordance with the fourth embodiment of the disclosure. The use of anexpander or tensor may impinge upon free axial movement of the electrodesupport structure 222 when the electrode support structure 222 isdiametrically impinged upon from a distal-most direction, for example.

Referring now to FIG. 12A, the proximal end portion 226 of each of theplurality of splines 224 of the electrode support structure 222 iscontained and constrained within a recess of an outer sheath 227. Theelectrode support structure 222 is in its collapsed arrangement.Referring now to FIG. 12B, the proximal end portion 226 of each of theplurality of splines 224 of the electrode support structure 222 arepartially advanced from the recess within the outer sheath 227, therebyallowing the electrode support structure 222 to partially return to itspreset shape. For example and without limitation, the proximal endportion 226 of each of the plurality of splines 224 of the electrodesupport structure 222 may be advanced out of the outer sheath 227 about0.125 inches (about 3.175 mm). Although this particular distance ismentioned in detail, the proximal end portion 226 of each of theplurality of splines 224 of the electrode support structure 222 may beadvanced out of the outer sheath 227 a greater or lesser amount inaccordance with various embodiments of the disclosure. The electrodesupport structure 222 may appear more spherical as it advanced out ofthe outer sheath 227. Movement of the proximal end portion 226 of eachof the plurality of splines 224 of the electrode support structure 222relative to the sheath 227 is configured to expand and collapse theelectrode support structure 222.

Referring now to FIG. 12C, the proximal end portion 226 of each of theplurality of splines 224 of the electrode support structure 222 arefully advanced from the recess within the outer sheath 227, therebyallowing the electrode support structure 222 to fully return to itspreset shape. For example and without limitation, the proximal endportion 226 of each of the plurality of splines 224 of the electrodesupport structure 222 may be advanced out of the outer sheath 227 about0.25 inches (about 6.35 mm). Although this particular distance ismentioned in detail, the proximal end portion 226 of each of theplurality of splines 224 of the electrode support structure 222 may beadvanced out of the outer sheath 227 a greater or lesser amount inaccordance with various embodiments of the disclosure. The electrodesupport structure 222 may appear substantially spherical as it is fullyadvanced out of the outer sheath 227.

Referring now to FIG. 13, a close up view of the distal end portion 228of each of the plurality of splines 224 of the electrode supportstructure 222 is generally illustrated. The distal end portion 228 ofeach of the plurality of splines 224 of the electrode support structure222 comprises a first connection element 229 configured to connect thedistal end portion 228 of one of the plurality of splines 224 to a firstadjacent spline 224 ₁. The distal end portion 228 of each of theplurality of splines 224 of the electrode support structure 222 furthercomprises a second connection element 231 configured to connect thedistal end portion 228 of one of the plurality of splines 224 to asecond adjacent spline 224 ₂. The first connection element 229 andsecond connection element 231 can each comprise a U-shaped member havingtwo substantially parallel legs 233 joined by a curved base 235. Each ofthe legs 233 are disposed substantially parallel to the axis (A) of theelectrode support structure 222. While the connection elements 229, 231are described as U-shaped having two substantially parallel legs 233joined by a curved base 235, the connection elements 229, 231 can takeany number of various other shapes in accordance with variousembodiments of the disclosure. The first connection element 229, secondconnection element 231, and each of the plurality of splines 224 areintegrally formed in accordance with the fourth embodiment of thedisclosure. Accordingly, the first connection element 229, secondconnection element 231, and each of the plurality of splines 224 areformed as a single, one-piece, unitary, monolithic structure. At least aportion of the distal end portion 228 of each of the plurality ofsplines 224 are disposed substantially along the axis (A) of theelectrode support structure 222.

Although at least four embodiments of this disclosure have beendescribed above with a certain degree of particularity, those skilled inthe art could make numerous alterations to the disclosed embodimentswithout departing from the spirit or scope of this disclosure. Alldirectional references (e.g., upper, lower, upward, downward, left,right, leftward, rightward, top, bottom, above, below, vertical,horizontal, clockwise, and counterclockwise) are only used foridentification purposes to aid the reader's understanding of the presentdisclosure, and do not create limitations, particularly as to theposition, orientation, or use of the disclosure. Joinder references(e.g., attached, coupled, connected, and the like) are to be construedbroadly and can include intermediate members between a connection ofelements and relative movement between elements. As such, joinderreferences do not necessarily infer that two elements are directlyconnected and in fixed relation to each other. It is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative only and not limiting.Changes in detail or structure can be made without departing from thespirit of the disclosure as defined in the appended claims.

Any patent, publication, or other disclosure material, in whole or inpart, that is said to be incorporated by reference herein isincorporated herein only to the extent that the incorporated materialsdoes not conflict with existing definitions, statements, or otherdisclosure material set forth in this disclosure. As such, and to theextent necessary, the disclosure as explicitly set forth hereinsupersedes any conflicting material incorporated herein by reference.Any material, or portion thereof, that is said to be incorporated byreference herein, but which conflicts with existing definitions,statements, or other disclosure material set forth herein will only beincorporated to the extent that no conflict arises between thatincorporated material and the existing disclosure material.

What is claimed is:
 1. An electrode support structure assemblycomprising: an electrode support structure comprising a plurality ofsplines, each of the plurality of splines having a proximal end portionand a distal end portion opposing the proximal end portion, wherein thedistal end portion of each of the plurality of splines comprises alongitudinal axis, and wherein each of the plurality of splines extendsfrom a proximal end to a distal end; a first element defining an axisand comprising an outer surface, wherein the outer surface comprises aplurality of slots configured to receive the distal end portion of eachof the plurality of splines, wherein the first element is configuredsuch that the distal end of each of the plurality of splines mayindependently move within the first element along the longitudinal axisof the spline and with respect to each of the other of the plurality ofsplines.
 2. The electrode support structure assembly of claim 1, whereinthe distal end portion of each of the plurality of splines comprises asection configured for engagement with the first element, wherein thesection comprises a shoulder.
 3. The electrode support structureassembly of claim 1, wherein a distal end of the distal end portion ofeach of the plurality of splines has an increased diameter relative tothe remainder of the distal end portion of each of the plurality ofsplines.
 4. The electrode support structure assembly of claim 1, whereinthe first element comprises a generally cylindrical member and whereinthe plurality of slots comprise grooves on the outer surface.
 5. Theelectrode support structure assembly of claim 4, wherein the groovesextend along the axis of the first element and are configured to alloweach of the plurality of splines to move along the axis of the firstelement a select distance.
 6. The electrode support structure assemblyof claim 1, further comprising a second element configured forengagement with the first element to retain the distal end portion ofeach of the plurality of splines within the plurality of slots of thefirst element, wherein the second element comprises a cap having atleast a portion thereof configured to be disposed radially outwardly ofthe first element.
 7. The electrode support structure assembly of claim6, wherein the cap further comprises an axial end and wherein the axialend is separated from the first element by a select distance to allowfor movement of each of the plurality of splines along the axis of thefirst element.
 8. The electrode support structure assembly of claim 1,further comprising a second element comprising a generally cylindricalmember having an outer radial surface including a plurality of channelsconfigured to receive the proximal end portion of each of the pluralityof splines.
 9. The electrode support structure assembly of claim 8,wherein the proximal end portion of each of the plurality of splinescomprises a section configured for engagement with the second element,wherein the section comprises a shoulder.
 10. The electrode supportstructure assembly of claim 8, wherein a proximal end of the proximalend portion of each of the plurality of splines has an increaseddiameter relative to the remainder of the proximal end portion of eachof the plurality of splines.
 11. The electrode support structureassembly of claim 1, wherein the first element comprises a cap having anaxial end and a radially extending wall and wherein each of theplurality of slots extend through the radially extending wall.
 12. Theelectrode support structure assembly of claim 11, wherein each of theplurality of slots extends along the axis of the first element and isconfigured to allow each of the plurality of splines to articulate froma first position in which the distal end portion of the spline isdisposed at a first angle relative to the axis of the first element to asecond position in which the distal end portion of the spline isdisposed at a second angle relative to the axis of the first element andwherein the first angle is different than the second angle.
 13. Theelectrode support structure assembly of claim 1, further comprising asecond element configured for engagement with the first element toretain the distal end portion of each of the plurality of splines withinthe plurality of slots of the first element, wherein the second elementcomprises a generally cylindrical member with an outer radial surfacehaving at least a portion thereof configured to be disposed radiallyinwardly of the first element.
 14. The electrode support structureassembly of claim 13, wherein the second element comprises a fluidcoupler having a first end configured to mate with the first element anda second end configured to mate with a tubing assembly.
 15. Theelectrode support structure assembly of claim 13, wherein the capfurther comprises an axial end and wherein the axial end is separatedfrom the second element by a select distance to allow for movement ofeach of the plurality of splines.
 16. The electrode support structureassembly of claim 1, wherein the plurality of splines includes a firstspline and a second spline, wherein the first spline includes a firstplurality of electrodes spaced apart on the first spline, wherein thesecond spline includes a second plurality of electrodes spaced apart onthe second spline, wherein each of the second plurality of electrodes onthe second spline is in a staggered position relative to the position ofeach of the first plurality of electrodes on the first spline.
 17. Theelectrode support structure assembly of claim 16, wherein at least oneof the second plurality of electrodes on the second spline is located onthe second spline at a position that is in substantially the same planeas the midpoint between two of the first plurality of electrodes on thefirst spline.
 18. The electrode support structure assembly of claim 16,wherein a first distance between a distal-most electrode of the firstplurality of electrodes and a distal end of the first spline issubstantially the same as a second distance between a proximal-mostelectrode of the second plurality of electrodes and a proximal end ofthe second spline.
 19. An electrode support structure assemblycomprising: an electrode support structure comprising a proximal end anda distal end and defining a longitudinal axis, wherein the electrodesupport structure is configured to be radially outwardly expandablerelative to the longitudinal axis to an expanded arrangement andradially inwardly collapsible relative to the longitudinal axis to acollapsed arrangement, the electrode support structure comprising: aplurality of splines, each of the plurality of splines having a proximalend portion and a distal end portion opposing the proximal end portion,wherein the distal end portion of each of the plurality of splinescomprises a longitudinal axis, wherein each of the plurality of splinesextends from a proximal end to a distal end; and a first elementdefining an axis and comprising an outer surface, wherein the outersurface comprises a plurality of slots configured to receive the distalend portion of each of the plurality of splines, wherein the distal endof each of the plurality of splines may independently move within thefirst element along the longitudinal axis of the spline and with respectto each of the other of the plurality of splines.
 20. An electrodesupport structure assembly comprising: an electrode support structurecomprising a plurality of splines, each of the plurality of splineshaving a proximal end portion and a distal end portion opposing theproximal end portion, wherein the distal end portion of each of theplurality of splines comprises a longitudinal axis, and wherein each ofthe plurality of splines extends from a proximal end to a distal end; afirst element defining an axis and comprising an outer surface, whereinthe outer surface comprises a plurality of slots configured to receivethe distal end portion of each of the plurality of splines, wherein thefirst element is configured such that the distal end of each of theplurality of splines may independently move within the first elementalong the longitudinal axis of the spline and may independently movewith respect to each slot.